It's an interesting document, but unless I misread it completely it pretty
much said that you shouldn't *want* to wrap independent, validated XML
within validated XML, since SGML, and thus XML, is meant to be used within
one document with one DTD, and that instead what you should want to do is
build the wrapped data by extending the wrapping DTD, or by not validating.
Since SOAP (or any other general purpose XML-based protocol) requires
exactly this capability, either the article's assumptions don't apply to us,
or we shouldn't be trying to use XML to build messaging layers. (I also
think that DTD's and namespaces are meaningful, but that's a separate
discussion or two.)
Personally, I think that while SGML was intended purely to encode individual
documents, XML has a broader application area, including use as a messaging
protocol that can transport arbitrary content, including valid XML. I admit
that I'm biased, in that I was part of a group (the ICE Authoring Group)
that built a protocol using XML that does just that, that's been in
production for a few years, and in general XML has worked out very nicely
for a whole raft of reasons that I am sure I don't need to elaborate on
here. So rather than deciding that XML shouldn't be used for messaging
protocols because this one issue is tricky, I'd prefer discussing options
for doing so, within practical constraints. For example:
- I don't think it's reasonable, or even desirable, to expect that all
industry DTD's will be rewritten to be extensions of SOAP (or any other
transport) -- the two layers should be independent.
- I don't think it's reasonable to limit XML message payloads to those that
do not include PCDATA.
- I don't think that it's reasonable to require packaging all message bodies
by reference, since that introduces a raft of serious security and
operational issues that are easily avoided by inline encoding in cases where
that's appropriate.
Did I miss anything?
----- Original Message -----
From: "S. Mike Dierken" <mike@knownow.com>
To: <xml-dist-app@w3.org>
Sent: Tuesday, October 24, 2000 2:36 PM
Subject: RE: XML within XML - includes, transcludes, whatever
> Good document. Eliot can always explain things better and in more depth
than
> I can.
>
> Mike
>
> > -----Original Message-----
> > From: xml-dist-app-request@w3.org [mailto:xml-dist-app-request@w3.org]On
> > Behalf Of Arjun Ray
> > Sent: Friday, October 06, 2000 11:25 PM
> > To: xml-dist-app@w3.org
> > Subject: Re: XML within XML - includes, transcludes, whatever
> >
> >
> > On Tue, 3 Oct 2000, S. Mike Dierken wrote:
> >
> > > [...] but XML already has an ID scoping mechanism - it is the
> > > 'document' concept. A document IS a scope.
This limitation is one of the reasons that ID's in XML aren't very useful.
> > Wow! I never thought that I would read this on a w3c list...
> >
> > > XML is a single document specification - it is a modular thing and
> > > multi-document concepts can be layered on top. There is no need to
> > > add more and more things into the base definition of XML. Many
> > > people have been using this internal-ref and external-ref approach
> > > for many years - just look at the Web.
> > [...]
> > > In short, I am against putting multi-document concepts into a
> > > single-document specification. There will always be a need to
> > > reference things outside the current document, and that mechanism
> > > is sufficient to deal with the problem.
> >
> > An echo from the past:
> >
> >
http://list.mc.duke.edu/scripts/WA.EXE?A2=ind9806&L=sgml-hl7&F=&S=&P=5337
> >
> > (If the link doesn't work - they're having problems with the server -
> > <URL:http://www.nyct.net/~aray/notes/wek-namespaces.txt> is a copy.)
> >
> >
> > Arjun
> >
>